Barium titanate crystals were grown by top seeded solution growth technique, nominally pure and also 0.05% and 1% Cr3+ impurity. We have conducted electron paramagnetic resonance (EPR) and photo-EPR studies at room temperature to investigate the role of Cr3+ impurity in photoinduced electron transfer. Nominally pure crystals contained Fe3+ as impurity, and its EPR is consistent with work reported by previous investigators. The Cr3+ doped crystals also contained Fe3+ impurities. It was observed that the site symmetry and the strength of the axial field parameter for Fe3+ complex were significantly different in Cr3+ doped crystals compared to nominally pure BaTiO3. The EPR spectra of Cr3+ were distinguished using the hyperfine structure of odd isotope 53Cr (I=3/2). By Photo-EPR technique we observe that in the presence of Cr3+, Fe3+ is not significantly photosensitive. In contrast Cr3+ exhibited higher photosensitivity in the presence of Fe3+. This was monitored by locking the magnetic field to 1/2↔1/2 transition of Cr3+, and recording intensity as a function of time, under insitu laser illumination. In lightly doped crystals the intensity of Cr3+ signal is sharply reduced immediately after switching the laser OFF showing non-exponential decay. In heavily doped crystals photo-EPR signal clearly shows that the fast decay of Cr3+ was followed by slow and steady build up of Cr3+ signal. The growth of Cr3+ signal was attributed to photoinduced decoupling of Cr3+ dimers. Thus, by doping BaTiO3 with Cr3+ more efficient grating formation can be achieved and time dependent phenomena are observed.
Lead magnesium niobate-lead titanate,
Pb(Mg, Nb)O3-PbTiO3 is a piezoelectric, ferroelectric crystal at room temperature with large electromechanical coefficient. The crystals were grown by PbO-B2O3 flux method. Typically the crystals were colorless and transparent, but a small fraction of them were Brown/reddish colored and show interesting photoluminescence (PL) properties. The PL studies were conducted under XeCl (308nm) excitation and under Argon Ion (Ar+) laser excitation. The excitation with 308nm gave broad PL centered at 500nm and intense emission at 710nm. The emission at 710nm in colorless crystals is very weak. The excitation with Ar+ laser coinciding with electronic absorption in brown samples gave rich and sharp PL particularly with 514.5 nm excitation. The PL with
514.5nm-Ar+ laserexcitation, consisted of intense anti stokes emission in addition to intense red and near infrared emission, is a result of photo-transfer optically stimulated luminescence (PT-OSL). This involved electron-hole recombination at photoinduced
magnetic polaron site. The PL emissions and the centers identified are the followings: 718nm emission due to magnetic polaron and 360nm emission due to cooperative emission from two polarons, Fe-R line at 660nm due to Fe3+ coupled to a cation; 380nm and 399nm due to Pb2+ clusters and Nb5+ center; 630 and 860 nm due to 6p→6s transition of Pb3+ and 760nm due to isolated Fe3+ ions. Raman spectrum of brown samples revealed the presence of nano particles/wires of orthorhombic β PbO. The FTIR spectrum gives evidence of significant amount of hydroxyl impurity.
Electron paramagnetic resonance (EPR) under the conditions of in situ laser illumination of the sample in the microwave
cavity, called photo-EPR is an excellent method to detect photo induced electron transfer in real time. We report Photo-
EPR results on the formation of clusters of magnetic ions in 0.67Pb(Mg1/3Nb2/3)O3. 0.33PbTiO3 (PMN-PT) on
illumination with blue laser at room temperature .The Photo EPR signal with g=2.00, agrees with Pb3+ formation. The
PMN-PT crystals 2-6mm size grown using PbO flux method were clear and transparent: and the upper part of the melt
yielded pink colored crystals containing a few hundred PPM of Fe3+ as seen by EPR Signal at g=4.3. The large linewidth
(~45 Gauss) of the photo-EPR signal and the presence of Fe3+ in the sample suggests the possibility of magnetic ion
cluster formation on blue laser excitation. When the photo-magnetic centers were produced in magnetic field of 7.5KG,
the signal was 30% more than that produced under switch-OFF condition of magnet having a remnant field of only 50G.
This critical observation is a clear pointer to the formation of photo-induced magnetic polarons at room temperature,
which are essentially clusters of ferromagnetically, coupled Fe3+ , Pb3+ and trapped electrons. The cluster formation and
decay exhibited fast optical response with growth and decay time less than or equal to 100msec. These observations show that PMN-PT
having excellent electromechanical properties can also be used for photomagnetic switching and real time holography
with fast grating response using Pb2+ <--> Pb3+ process. PMN-PT would have additional advantage compared to other
photo-refractive materials: due to possibility that the grating contrast can be manipulated by external magnetic field.
We discuss phenomena of the optical photons and charged particle channeling in the periodic structures. While particle (as protons) channeling is widely used for the characterization of defects in crystals, channeling of photons is less known. We have demonstrated feasibility of optical channeling method for copying of phase radial grating on the chalcogenide semiconductor glass film and photo-thermoplastic films (PTPF). Chalcogenide glassy semiconductors (CGS) as a medium for recording of optical information have some advantages such as the possibility of achieving a higher resolution power, stability, and a high photosensitivity. We report about recording of the radial phase grating in the doped As-S-Se (CGS). Radial grating was recorded by making copy from the master phase grating placed in the near-field zone and exposure to the CW green (λ=532 nm) low power (P=100 mW) solid-state laser or incoherent UV source. The exposure time has been varied from 15 to 30 min. The recording process could be explained by optical channeling. This phenomenon gives us an opportunity to create phase radial grating using coherent and incoherent illumination.
We have measured the rc (effective electrooptical coefficient) of pure and doped Ferroelectric Lithium Niobate (LN) using a single beam, null detection polarimeter. The polarimeter is adjustable between two adaptive optics configurations--an iris hard stop beam pattern on the one hand and a diffractive optics generated top-hat beam on the other. We clearly show the need to control thermal heating of LN due to the transmitted laser beam. The required heating control has been implemented using a fabricated metallic heat sink called a "Cold Finger." In addition to its electrooptical properties, LN possesses a combination of unique piezoelectric, pyroelectric, and photorefractive properties. These properties make it suitable for applications in optical devices as frequency doublers, modulators, switches, and filters in communication systems and holographic recording medium. We present the classical microscopic anharmonic oscillator description for generating Pockels coefficients, and briefly describe the polarimetry measurement system. Here, the growth of pure and iron doped lithium Niobate is also described using an Automatic Diameter Control Czochralski Design growth technique. The results of growth, electrooptic measurements, adaptive optics implementation and some physical properties are compared and presented.
Short pulse spectral content becomes modified while propagating in dispersive media. However, in dispersive nonlinear media, optical pulses resulting in solitary waves maintain their existence if proper balance is established between nonlinear self-phase modulation on the one hand and linear dispersion on the other. Such invariance pulse shape is critical for data transfer reliability in telecommunication technologies. Robust solitary waves that emerge from collisions unaltered are called solitons. During propagation of optical solitons in inhomogeneous media their trajectories are observed to deviate from straight-line paths to that of oscillatory behavior. Here, we use a spatial optical soliton solution to the nonlinear Schrödinger equation in an inhomogeneous triangular refractive index profile as a small index perturbation to illustrate the oscillation motion. We determine the effective acceleration, give the period of oscillation, and compare results with the Gaussian refractive index profile. Such spatial solitons behave as point masses existing in a Newtonian gravitational potential hole. This novel transverse oscillatory behavior, occurring for various refractive index profiles, results from an effectively bounded acceleration.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.